Chemical constituents of <i>Citrus grandis</i> (L.) Osbeck (Rutaceae) and their α-glucosidase inhibitory activity

Abstract

The chemical investigation of the methanolic bark extract of <i>Citrus grandis</i> (L.) Osbeck (Rutaceae) led to the isolation of one saponin named aridanin (<b>1</b>) isolated for the first time in the genus <i>Citrus</i>, together with seventeen known compounds including eight acridone-type alkaloids, two limonoids, two coumarins, one sugar, one lactam derivative, and three common steroids. Their structures were conclusively established using 1D- and 2D-NMR spectral data. The isolated compounds 1-9 were tested for their α-glucosidase inhibitory activity and the results showed that they all have potency higher than the reference acarbose (IC<sub>50</sub> = 218.2 ± 2.8 μM) and aridanin was the strongest one which could be due to its sugar unit as usually observed for triterpene saponins. Furthermore, the structure-activity relationship of the tested compounds has been discussed as well as the chemotaxonomic significance of the study. The present study enriches the chemistry of <i>Citrus</i> with three additional compounds (1, 14, 15) and classifies the plant <i>C. grandis</i> as a good source of leads for the development of anti-diabetic drugs.